#define _CRT_SECURE_NO_WARNINGS 1

class Solution {
public:
    int peakIndexInMountainArray(vector<int>& arr) {
        int left = 0, right = arr.size() - 1;
        while (left < right)
        {
            int mid = left + (right - left) / 2;
            if (mid + 1 < arr.size() - 1 && arr[mid] < arr[mid + 1]) left = mid + 1;
            else right = mid;
        }
        return left;
    }
};